The overall objective of this proposal is to develop an understanding of fundamental principles that govern the ultimate configuration of complex multi-subunit aggregates and the processes by which they are assembled. Such macromolecular assemblages include ribosomes, viruses, multi-enzyme complexes, muscle filaments, nuclear pores and many other components of biological systems that play important roles in health problems. Many of these structures are symmetric or quasi-symmetric aggregates of chemically distinct subunits. The giant respiratory proteins of invertebrates are constructed in an intricate hierarchy of symmetries. These molecules illustrate many rather general assembly principles and they will be principal objects of study in this investigation. The specific aims for the proposed research include both theoretical and experimental approaches. (1) The theoretical study will concern the bonding properties needed for spontaneous, self-limited assembly. Appropriately detailed models will be built to facilitate the analysis. The acetylcholine receptor, proton ATPase and phycobiliproteins will be considered as well as the giant hemoglobins and hemocyanins. (2) The experimental work will primarily concern the structure analysis of annelid hemoglobins. Electron microscopy will be used to test models developed in the theoretical study. X-ray crystallography will be used to analyze the four-million dalton hemoglobin from earthworms. (3) Biochemical isolation and characterization of distinctive substructures of annelid hemoglobins will also be carried out. Finally, (4) attempts will be made to crystallize the well characterized hemocyanins from scorpions and tarantulas.